U.  S.  Department  of  Agriculture,  Forest  Service 

FOREST   PRODUCTS   LABORATORY 

In  cooperation  with  the  University  of  Wisconsin 
MADISON,  WISCONSIN 


COMPARATIVE  TESTS  OF  WHITE  OAK 
AND  DOUGLAS  FIR  BARRELS 

By   T.  R.  C.  WlLSOfj_ 
Engineer  in  Forest   Products 


cn 


March,    1925 


Digitized  by  the  Internet  Archive 

in  2013 


http://archive.org/details/comtestsOOfore 


COMPARATIVE  TESTS   OE  WHITE  OAK  AIT)  DOUGLAS  EIR  BARRELS 


Py 


T.  R.  C.  WILSON 
Engineer  in  Eorcst  Products 


This  report  is  a  comparative  summary  of  two  series  of  tests 
performed  at  the  U.  S.  Forest  Products  Laboratory?  Madison*  Wis. 
one  on  Douglas  fir  "barrels,  conducted  during  March,  19.21,  and  the  other 
on  white  oak  barrels,  conducted  several  years  earlier  and  first  reported 
in  U.  S.  Department  of  Agriculture  Bulletin  No.  86. 

The  oak  barrels,  furnished  by  the  St.  Louis  (Mo.)  Cooperage 
Co.,  were  43  in  number  and  were  divided  into  six  groups  of  eight.,  as 
follows:   Group  Ho.  1  of  5/8-inch  stock,  with  6  hoops;  group  Ho.  2, 
5/3-inch  stock,  8  hoops;  group  Ho.  3,  3/4-inch  stock,  6  hoops;  gro 
Ho.  4,  3/4-inch  stock,  8  hoops;  group  No.  5,  7/8-inch  stock;  6  hoops; 
group  Ho.  6,  7/8-inch  stock,  8  hoops.  The  material  was  quarter-sawed 
white  oak, .practically  straight  grained,  and  free  from  defects.  1 
barrels  were  of  excellent  workmanship  and  were  well  coated  v. ith  paraf- 
fin inside.  The  staves  varied  in  width  from  about  2  0/2  inches  to 
about  7  inches  .  The. heads  were  as  a  rule  composed  of  four  pieces 
joined  together  with  6-1/ 6-inch  hickory  dowels.  Two  heads  were  composed 
of  three  pieces  each. 

The  Douglas  fir  barrels,  furnished  oy   the  Western  Cooperage 
Co.,  of  Portland,  Ore.,  were  33  in  number  and  were  divided  into  three 
groups  of  eleven,  which  the  company  in  their  forwarding  letter  described 
in  the  following  terms:   "The  stock  in  these  packages  is  sawn  from  Ho.  1 
Douglas  fir  timber  and  represents  our  No*  1  grade  3/4-  inch  oil  staves 
and  our  Ho.  1  grade  20-7/i6-inch  heading  in  3/4  and  15/l6-inch  thick- 
ness. There  are  to  be  33  barrels  forwarded  to  Madison.  Eleven  of  these 
are  hooped  with  6  hoops  and  headed  with  3/4-inch  head;  11  are  hooped 
with  8  hoops  and  headed  with  3/4-inch  heads;  and  the  balance  are  hooped 
with  8  ho^ps  and  headed  with  15/l 6-inch  heads.   All  headings  used  in 
these  packages  have  glued  joints,  and  the  packages  were  set  up  from 
average  scock  the  some  as  received  from  our  mill,  there  being  no 
special  selecting,," 

The  barrels,  of  both  species,  after  being  completely  filled 
with  water ?  were  subjected  to  the  following  tests:   Side  compressic  j 
diagonal  compression,  internal  pressure,  side  drop,  and  diagonal  drop. 
Some  barrels  of  each  group  and  each  species  were  subjected  to  each  kind 
of  test.   The  results  will  be  briefly  discussed  in  the  succeeding 
paragraphs  and  the  general  conclusions  stated. 

678 


Oak  Barrels 

In  each  kind  of  tost   the  first  water  to  appear  on  the  outside 
of  the  "barrel  was  usually  from  seepage  lengthwise  through  the  pores  of 
the  wood  at  the  chime.     The  first  leak  usually  occurred  either  between 
the   staves  and  the  head  or  between  the  staves  at   the  chime.     In  all   the 
tests  except  internal  pressure  the  first  leak  was  usually  coincident 
with  the   slipping  of  the   staves. 

In  the  internal-pressure  test  there  were  two  general  classes 
of  failures:      (l)  By  springing  and  breaking  of  the  head;    and  (2)     by 
leaking  between  the   staves  at  the  bilge. 

In  the  diagonal-compression  test   the  failure  was  a  general 
failure  of  the  head  combined  with  slipping  of  the   staves.      In  the 
side-compression  test   the  failure  was  a  general   leaking  at   the  head  ; 
and  slipping  of  the   staves  followed  by  the  breaking  of  the  staves  at 
the  bilge. 

In  the   side-drop  test  the  slipping  of  the   staves  caused 
loosening  of  hoops  and  leakage  at  heads,   followed  by  breaking  of  the 
staves  at   the  bilge.     In  three  of   the   six  barrels  thus  tested,   failure 
was  due  to  the  heads  being  broken  or  forced  out  by  the  pressure 
produced  by  the  impact. 

The  lower  heads  of  all  barrels  tested  by  drc  3ping  r;i  the 
chime  were  broken  or  forced  out  by  the  pressure  due    c:    the  i.npact. 


Douglas  Fir  Barrels 

First  leakage  in  nearly  all   tests  of  Douglas  fir  barrels 
developed  in  one  of  two  ways:      (l)  By  water  passing  completely  around 
the  edge  of  the  head  and  appearing  in  the  angle  between  the  head  and 
the  chime,    or  (2)  by  water  passing  partially  around  the  edge  of  the 
head  and  thence  through  the  pores  and  appearing  as   small  drops  on  the 
edge  of  the  chime.     Leakage  of  the  first  type  is   aescribed  as   "leakage 
at  croze,"  and  the  second  as   "seepage  through  cl'.me."     There  were  very 
few  instances  in  which  leakage  between  the  staves  occurred  except 
after  the  barrel  had  beon  quite    severely  deformed  as   in  the   side  and 
diagonal-ccmpression  tests.  In  the  diagonal-compression  tests  1 

age  due  to    -rushing  at   the  edge  of   the  head  occurred  at  a  fairly  ea_*lj 
stage.     A'    a  special   test,  barrel  No.   13  was   so  placed  that  the  end 
grain  of   the  head  came  at   the  point   of  pressure,    and  leakage   did  not 
occur  until   a  considerably  higher  load  was   reached. 

Aside  from  the  first  leakage,   types  of  failures  differed 
with  the  kind  of   test. 


678  _2- 


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In  side  and  diagonal-compression,  later  failures  were  "by- 
slipping  in  stave  joints  and  shear  or  splitting  of  staves,  combined 
with  opening  of  the  joint  "between  staves  and  head  and  splitting  of 
head.   In  this  test  there  were  numerous  instances  in  which  staves  split 
or  sheared  for  their  entire  length.   In  fact,  it  seemed  to  "be  almost 
as  easy  for  such  shearing  to  occur  as  for  staves  to  slip  on  each  other 
at  the  joints.   This  was  true  also  in  side  and  diagonal-drop  teste. 

Final  failure  in  side  and  diagonal-drop  tests  was  the  driving 
out  of  the  head  "by  the  shock  of  the  contents. 

Final  failure  in  internal-pressure  tests  was  "by  "breaking  or 
"bursting  out  of  the  heads. 


Comparison  of  White  Oak  and  Douglas  Fir  Barrels 

At  first  leak  in  side  compression,  the  Douglas  fir  "barrels 
take  only  about  two-thirds  of  the  load  carried  "by  the  white  oak 
"barrels.   The  white  oak  "barrels,  however,  "begin  leaking  at  a  much 
smaller  deformation  than  do  the  Douglas  fir,  and  the  product  of  load 
and  deflection  at  first  leak  is  in  every  case  of  comparison  higher 
for  Douglas  fir  than  for  white  oak.  These  facts  indicate  that  when 
subjected  to  shocks  against  the  "bilge,  the  Douglas  fir  "barrels,  al-. 
though  they  develop  less  resistance  before  leakage,  yield  much  more 
(or  farther)  and  can  absorb  fully  as  great  a  shock  as  the  white  oak. 
It  should  be  noted  in  this  connection  that  a  common  practice  is  to 
store  or  stow  barrels  on  their  sides  with  the  bottom  row  blocked  at 
the  quarters  and  upper  rows  laid  in  the  "cantlines,11  or  space  between 
barrels  of  the  row  below,  and  with  the  bilges  above  the  heads  of  the 
row  below.   It  is  to  be  expected  that  barrels  so  arranged  will  sustain 
considerably  larger  loads  than  were  developed  in  the  side  compression 
test. 

At  first  leak  in  diagonal  compression,  Douglas  fir  barrels 
take  less  load  than  white  oak  barrels.   Here  again,  however,  white  oak 
barrels  stand  much  less  deformation  than  the  Douglas  fir,  with  the 
result  that  shock-resistance  as  indicated  by  product  of  load  and 
deflection  is  practically  equal  for  barrels  of  the  two  species. 

The  height  of  drop  (both  side  and  diagonal)  for  Douglas  fir 
barrels  at  first  leak  averages  about  three-fourths  as  much  as  for  the 
white  oak.  Approximately  the  same  ratio  applies  to  height  of  drop  to 
produce  leakage  at  the  rate  of  one  pound  of  water  per  minute. 

When  subjected  to  internal  water  pressure  the  Douglas  fir 
barrels  develop  two  to  three  times  as  great  pressure  at  first  leak 
as  do  the  white  oak  barrels..  The  pressure  required  to  produce  leakage 
at  the  rate  of  1  pound  of  water  per  minute  averages  about  30  percent 
higher  for  Douglas  fir  than  for  white  oak. 

67S  -3- 


Discussion  and  Conclusions 

The  following  conclusions  apply  only  to  white  oak  and  Douglas 
fir  barrels  having  the  combination  of  number,  quality,  and  dimensions 
of  hocps  and  thicknesses  of  staves  and  heads  represented  in  the  tests 
and  described  herein: 

1.  In  the  oak  barrels,  increase  in  thickness  of  stave  is  of 
much  less  value  than  increase  in  head  thickness,  and  it  is  to  be  ex- 
pected that  oak  barrels  with  5/2-inch  staves  and  7/S-inch  or  15/16- 
inch  heads  v/ill  prove  fully  as  serviceable  under  ordinary  conditions 
as  barrels  with  7/8-inch  staves  and  7/8-inch  heads* 

2.  In  Douglas  fir,  barrels  with  15/l6-inch  heads  and 
3/U-inch  staves  are  somewhat  superior  in  resistance  to  internal  pres- 
sure to  barrels  with  3/^~inch  heads  and  staves, 

3.  When  there  is  little  change  in  moisture  content  of  the 
wood,  as  in  these  tests,  the  eight-hoop  barrels  show  but  little 
superiority  ov^r  six-hoop.  When  barrels  are  subjected  alternately 
to  moist  and  dry  conditions,  with  the  consequent  tendencies  of  the 
staves  to  swell  and  shrink,  it  is  to  be  expected  that  the  advantage 
of  the  eight-hoop  barrels  will  be  enhanced, 

H.  When  barrels  of  both  species  are  well  and  carefully 
made  of  properly  selected  stock,  they  compare  as  follows: 

Douglas  fir  barrels  have  about  two-thirds  as  great  resistance 
as  have  white  oak  barrels  to  leakage  under  steady  loads,  as  in  the 
bottom  of  storage  piles.   The  Douglas  fir  barrels,  however,  probably 
have  sufficient  resistance  to  carry  safely  such  loads  as  are  at  all 
likely  to  come  on  them  in  storage  or  shipment.   The  Douglas  fir 
barrels,  moreover,  can  be  deformed  to  a  greater  extent  without  leakage 
than  can  the  white  oak.  Resistance  to  shock  is  proportional  to  the 
product  of  load  and  deformation.  Douglas  fir  and  white  oak  barrels 
are  practically  equal  in  this  respect,  a  fact  indicating  that  when 
loaded  on  end  in  railway  cars  they  may  be  expected  to  withstand  equal 
shocks  without  leaking.  After  leakage  has  begun,  however,  the 
steady  force  and  the  shock  required  to  cause  increased  leakage  a.re 
greater  for  white  oak  than  for  Douglas  fir  barrels. 

When  dropped  upon  the  chime  or  upon  the  bilge,  the  Douglas 
fir  barrels  withstand  without  leakage  about  25  per  cent  lower  drops 
than  white  oak,  indicating  somewhat  greater  susceptibility  to  damage 
from  rough  handling  in  rolling  or  sliding  down  skids. 

The  Douglas  fir  barrels  withstand  from  two  to  three  times  as 
much  internal  pressure  before  leaking  as  do  the  white  oak  barrels. 


67S  -k- 


•    '    :  •  '  '■ 


5.   The  Douglas  fir  barrels  tented  were  made  with  17-gauge 
"by  1-3/U-inch  and  18-gauge  by  l-l/ 2-inch  hoops  in  order  to  have  them 
uniform  in  this  respect  with  the  oak  barrels  tested,  and  also  to 
comply  with  I.  C.  C.  specification  No.  10.  As  Douglas  fir  is  softer 
and  exerts,  less  force  in  swelling  than  oak,  it  is  not  certain  that 
these  sizes  arc  necessary.   Further  tests  would  be  required  to  deter- 
mine the  safe  and  most  economical  size  of  hoops  for  Douglas  fir  barrels. 

In  connection  with  these  comparisons  of  white  oak  and  Douglas 
fir  barrels  it  is  to  be  remembered  that  all  the  barrels  tested  were  of 
selected  stock  and  well  manufactured.   The  oak  staves  and  heading  were 
white  oak,  which  is  much  more  resistant  than  red  oak  to  penetration 
by  liquids.  Because  of  this  quality  and  other  properties,  such  as 
great  stability  of  form  and  shape  under  changing  moisture  conditions 
and  greater  resistance  to  decay,  white  oak  clear  of  sapwood  is 
recognized  as  much  superior  to  red  oak  for  barrel  making*  The  Douglas 
fir  barrels  were  from  timber  selected  for  its  special  suitability  for 
barrel  manufacture.  These  points  are  mentioned  to  bring  out  the  fa 
that  the  barrels  tested  were  such  as  can  be  made  only  through  careful 
attention  to  selection  of  timber  and  to  manufacturing  details,  and 
that  the  barrels  were  of  comparable  quality  in  their  respective 
species. 

The  results  of  the  tests  lead  to  the  conclusion  that  with 
carefully  selected  timber  and  carefully  manufactured  barrels,  white 
oak  will  excel  Douglas  fir  barrels  in  serviceability  under  ordinary 
shipping  conditions.  If,  however,  the  white  oak  barrels  are  of 
indifferently  selected  stock  containing  sapwood  or  defects,  or  are 
carelessly  manufactured,  they  may  be  expected  to  render  much  poorer 
service  than  Douglas  fir  barrels  well  made  of  properly  selected 
material. 


Selection  and  Handling  of  Material 

Timber  is  selected  and  stock  handled  with  great  care  by  the 
larger  manufacturers  of  Douglas  fir  barrels,  and  it  is  well  to  consider 
here  a  number  of  points  bearing  on  the  making  of  barrels  of  the  best 
quality  from  the  species.   These  points  have  been  developed  from  the 
experience  of  manufacturers,  observation  of  the  barrel  tests  described 
herein,  mechanical  tests  of  Douglas  fir,  and  field  observations  of  the 
properties  and  peculiarities  of  the  species. 

1.  It  is  believed  'oy   barrel  manufacturers  that  material  of 
suitable  character  can  be  secured  only  from  trees  grown  in  the  low- 
lying  regions  or  so-called  fog  belts. 

2.  Staves  of  the  Douglas  fir  barrels  tested      n  average 
of  about  23  annual  growth  rings  per  inch.   The  minimum  number  was  7 


678  „5_ 


and  the  maximum  UU.      It   would  "be  well   to   require   that   staves   chow  not 
less  than  8  growth  rings  per  inch* 

3.      It   is   recommended  that  Douglas  fir  bolts  "be   converted 
into  staves  and  kiln-dried  promptly  after  cutting  from  the  logs,   in 
order  to  avoid  the   rather  rapid  deterioration  that  may  occur  through 
the   checking  of   short  bolts   in  drying, 

H,      It   is   of  prime   importance   that   the   staves  be   as   nearly 
as  possible  perfectly  quarter-sawed  or  edge-grained*      Incipient  ring 
shake  or  weakness   of  bond  between  the  annual   rings/rather  frequently 
encountered  in  Douglas  fir.      Where   this   occurs   in  a  stave  having  the 
plane  of   the  annual   rings   striking  through  its  axis  at  angle  of  less 
than  about   GO  degrees  with  its   surface,    slippage  along  the  rings 
having  such  weakness   is  very  likely  to  haopen.      It   is   recommended 
that  in  specifications  for   tight  barrels  of  Douglas  fir  a  limit 
be   set   to  the  deviation  from  perfect  edge  grain.      The  following  is 
suggested  as  a  simple  and  practical  statement   of  the  allowable  devia- 
tion; 

"Staves   shall  be   so  manufactured  that   the  annual   rings  at 
any  point   do  not   deviate  from  a  line  perpendicular  to   the  face   of   the 
stave  by  more   than  one-half   of   the   thickness   of   the   stave f" 

5,      Cutting  of   staves   in  the  manner  recommended  has   a  further 
advantage,    since  the  shrinkage  in  width  of   quarter-sawn  stock  averages 
only  from  one-half   to   two-thirds   that   of   slash-grain  material.     Barrels 
made  of   quarter-sawn  staves  therefore   shrink  and  swell  less  with  change 
in  atmospheric  and  moisture  conditions  and  give  less  trouble  with  leak- 
age,  regardless  of   species.     Hot  only  strength  properties  but  also  the 
tendency  to   shrink  and  swell   are  factors   that   should  be   considered  in 
estimating  the   suitability  of  a  given  species   for  tight   cooperage.      The 
shrinkage  or  swelling  of  quarter-sawn  stock  with  change  of  moisture 
content  is  practically  the   same  for  oak  and  Douglas  fir.      Consequently 
it   is   to  be  expected  that   troubles  from  this   source  will  be  least   for 
the  barrels  whose   staves  are  most  perfectly  quarter-sawn. 


67S  -6- 


UNIVERSITY  OF  FLORIDA 


ii  ii  mil 

3  1262  08929  1719 


